This invention relates to an automatic planing machine particularly being capable of eliminating back-lash during a feeding operation and carrying out a thickness determination work for a workpiece with high precision, and including a simplified driving mechanism, and more particularly to an automatic wood planing machine for cutting a wood workpiece.
An automatic planing machine is generally provided with a cutter block disposed above a table or stool, and a plurality of feed rollers for feeding a workpiece are disposed at the front and rear sides thereof. The workpiece such as wood is automatically fed by the feed rollers along the table and the workpiece is cut during this feeding operation. Such an automatic wood planing machine is disclosed, for example, in Japanese Patent Publication No. 20341/1987.
An improved automatic wood planing machine is also disclosed in Japanese Patent Publication No. 25481/1987, in which two auxiliary rollers are arranged on the side of the table in a manner opposing to the feed rollers. The feed rollers press the workpiece against the auxiliary rollers, whereby the workpiece can be fed with the workpiece clamped between these rollers. Furthermore, the automatic wood planing machine has a roller case for the feed rollers which is moved towards or away from the stool so as to set dimensions of the workpiece. The roller case is always urged by a long compression coil spring in a direction that the roller case is apart from the table to precisely set the dimensions of the workpiece. In addition, the driving system of the automatic wood planing machine comprises a motor having a a driving shaft having an end to which a pulley is secured to thereby transmit the rotation of the motor driving shaft to the cutter block by means of a belt. A speed reduction mechanism is mounted on the extension of the driving shaft of the speed reduction mechanism is transmitted to the feed rollers by means of chains.
However, in one aspect of such a conventional automatic wood planing machine of the characters described above, as shown in FIGS. 17 and 18, a front and a rear auxially rollers 102a, 102b are rotatably supported by a plurality of bearings which are simply fixed to a stool 103 and which are not urged toward a front and a rear feed rollers 101a and 101b. At the beginning of work or finishing for a workpiece A, as shown in FIG. 17, the workpiece A is strongly pushed by the front feed roller 101a toward the front auxially roller 102a with the workpiece A being not pushed by the front feed roller 101b. At the end of work, the workpiece A is pushed by the rear feed roller 101b toward the rear auxially roller 102b with the workpiece A being not pushed by the front feed roller 101a. Therefore, the front and rear portions of the workpiece A are deformed upwardly, so that those portions thereof are cut deeply by a cutter block 104 to form two thin portions a.sub.1 and a.sub.2 on the workpiece A. Further, since the auxially rollers 102a and 102b or pressure rollers are slightly projected from the guide surface of the stool 103, when a thickness determination work for setting a thickness of the workpiece A is performed, precision of thickness is decreased.
In another aspect of the conventional automatic planing machine, when the long compression coil spring is utilized, the spring force changes according to the size of the gap between the roller case and the table, which results in that the dimension setting stability cannot be maintained.
In still another aspect of the conventional automatic wood planing machine, in the driving mechanism thereof, since the speed reduction mechanism is mounted at a portion apart from the driving motor, the automatic wood planing machine becomes bulky. Further, since the output shaft of the speed reduction mechanism is connected to the feed rollers via a chain, precision in a thickness determination work for the workpiece is degraded.